This project is concerned with the study of mechanisms by which various ganglion cells of the retina attain distinctive dendritic patterns during normal development, following partial or complete ablation of the eye or target center (the optic tectum), and following reduction in ganglion cell densities induced chemically. The formation of the adult pattern of cell density distribution, and the developmental sequence of dendritic elaboration will be evaluated by utilizing a recently developed method for in vitro application of horseradish peroxidase (HRP) to optic axons. Methods include light microscopy of flatmounted retinae, sectioned retinae, retrograde HRP transport, Nissl staining, kainic acid administration to selectively ablate retinal cells. These experiments will be performed on embryonic and yound adult chicken. The proposed experiments will determine the developmental sequence of identifiable retinal ganglion cells and their dendritic elaborations. In addition, experiments are proposed to determine whether the extent of the dendritic field is dependent upon the availability of presynaptic elements, i.e., amacrine and bipolar cells, or is independent of such factors. The proposed experiments will seek the mechanisms responsible for limiting the dendritic field sizes. The proposed study will provide detailed information and evidences for cellular interactions during the formation of dendritic fields in the developing and maturing retina.